A coil having a longitudinal coil housing is described in German Patent No. DE 200 12 401 U1. A plurality of preassembled modules or components are installed inside the coil housing. Among these components are, for example, a rod-shaped magnetic core, which is concentrically surrounded by a secondary coil shell having a secondary winding, and by a primary coil shell having a primary winding. Once the components and modules have been assembled and installed inside the coil housing, the coil housing is filled with an insulating resin. Such an ignition coil is installed in the cylinder head of the engine into a corresponding receiving bore and brought into contact with the spark plug of the internal combustion engine. Since the space in the cylinder head of the internal combustion engine is limited, the receiving bore for the ignition coil is likewise limited in its diameter. This is in conflict with the requirement of providing the highest possible ignition energy for the spark plug because this would require a spark plug whose diameter is also as large as possible with respect to the available space.
In addition, a primary wire winding for a rod-type ignition coil that is optimized with respect to its installation space is described in German Patent No. DE 102 47 411. In a first working step, the primary wire for a primary winding is wound onto a mandrel, which simultaneously serves as internal component for an injection-molding die. The primary winding including the mandrel is then extrusion-coated by plastic, the plastic simultaneously forming the outer housing of the rod-type ignition coil. Thus, the known primary winding enables a very advantageous design with regard to its radial extension because a separate primary coil shell that enlarges the diameter of the rod-type ignition coil, as well as an outer housing are dispensed with.